CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $)	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2009	$ 172,577,000	$ 92,000	$ 750,158,000	$ (577,267,000)	$ (406,000)
Balances (in shares) at Dec. 31, 2009		92,521,946
Increase (Decrease) in Stockholders' Equity
Net loss	(111,377,000)			(111,377,000)
Other comprehensive income	310,000				310,000
Issuance of common stock in connection with public offering, net of issuance costs of $6,300	93,700,000	20,000	93,680,000
Issuance of common stock in connection with public offering, net of issuance costs of $6,300 (in shares)		20,000,000
Issuance of common stock in connection with private offering, net of issuance costs of $44	9,956,000	4,000	9,952,000
Issuance of common stock in connection with private offering, net of issuance costs of $44 (in shares)		4,181,481
Stock-based compensation related to issuance of common stock and options in exchange for services	11,687,000	2,000	11,685,000
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		1,994,993
Issuance of common stock under equity plans, net of cancellations of non-vested restricted stock	551,000	4,000	547,000
Issuance of common stock under equity plans, net of cancellations of non-vested restricted stock (in shares)		3,654,057
Stock-based compensation for equity-based awards to employees and directors	13,718,000		13,718,000
Distribution to TA Therapeutics, Ltd. shareholder	(6,000)			(6,000)
401(k) contribution	1,619,000	1,000	1,618,000
401(k) contribution (in shares)		264,252
Balances at Dec. 31, 2010	192,735,000	123,000	881,358,000	(688,650,000)	(96,000)
Balances (in shares) at Dec. 31, 2010		122,616,729
Increase (Decrease) in Stockholders' Equity
Net loss	(96,853,000)			(96,853,000)
Other comprehensive income	5,000				5,000
Issuance of common stock in connection with acquired in-process research technology	28,094,000	5,000	28,089,000
Issuance of common stock in connection with acquired in-process research technology (in shares)		5,261,144
Stock-based compensation related to issuance of common stock and options in exchange for services	715,000		715,000
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		180,954
Issuance of common stock under equity plans, net of cancellations of non-vested restricted stock	3,263,000	3,000	3,260,000
Issuance of common stock under equity plans, net of cancellations of non-vested restricted stock (in shares)		3,031,121
Stock-based compensation for equity-based awards to employees and directors	15,249,000		15,249,000
Debt discount in connection with warrant issuances	1,715,000		1,715,000
401(k) contribution	1,680,000		1,680,000
401(k) contribution (in shares)		353,200
Balances at Dec. 31, 2011	146,603,000	131,000	932,066,000	(785,503,000)	(91,000)
Balances (in shares) at Dec. 31, 2011	131,443,148	131,443,148
Increase (Decrease) in Stockholders' Equity
Net loss	(68,881,000)			(68,881,000)
Other comprehensive income	131,000				131,000
Stock-based compensation related to issuance of common stock and options in exchange for services	135,000		135,000
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		170,298
Cancellation of non-vested restricted stock under equity plans, net of issuances of common stock	267,000	(2,000)	269,000
Cancellation of non-vested restricted stock under equity plans, net of issuances of common stock (in shares)		(2,592,375)
Stock-based compensation for equity-based awards to employees and directors	5,311,000		5,311,000
401(k) contribution	2,087,000	1,000	2,086,000
401(k) contribution (in shares)		1,221,624
Balances at Dec. 31, 2012	$ 85,653,000	$ 130,000	$ 939,867,000	$ (854,384,000)	$ 40,000
Balances (in shares) at Dec. 31, 2012	130,242,695	130,242,695